title: Molecular basis of 9G4 B cell autoreactivity in human systemic lupus erythematosus.
abstract: 9G4(+) IgG Abs expand in systemic lupus erythematosus (SLE) in a disease-specific fashion and react with different lupus Ags including B cell Ags and apoptotic cells. Their shared use of VH4-34 represents a unique system to understand the molecular basis of lupus autoreactivity. In this study, a large panel of recombinant 9G4(+) mAbs from single naive and memory cells was generated and tested against B cells, apoptotic cells, and other Ags. Mutagenesis eliminated the framework-1 hydrophobic patch (HP) responsible for the 9G4 idiotype. The expression of the HP in unselected VH4-34 cells was assessed by deep sequencing. We found that 9G4 Abs recognize several Ags following two distinct structural patterns. B cell binding is dependent on the HP, whereas anti-nuclear Abs, apoptotic cells, and dsDNA binding are HP independent and correlate with positively charged H chain third CDR. The majority of mutated VH4-34 memory cells retain the HP, thereby suggesting selection by Ags that require this germline structure. Our findings show that the germline-encoded HP is compulsory for the anti-B cell reactivity largely associated with 9G4 Abs in SLE but is not required for reactivity against apoptotic cells, dsDNA, chromatin, anti-nuclear Abs, or cardiolipin. Given that the lupus memory compartment contains a majority of HP(+) VH4-34 cells but decreased B cell reactivity, additional HP-dependent Ags must participate in the selection of this compartment. This study represents the first analysis, to our knowledge, of VH-restricted autoreactive B cells specifically expanded in SLE and provides the foundation to understand the antigenic forces at play in this disease.
authors.affiliation: Division of Allergy, Immunology and Rheumatology, University of Rochester School of Medicine, Rochester, NY 14642;
authors.forename: Christopher
authors.initials: C
authors.lastname: Richardson
authors.forename: Asiya Seema
authors.initials: AS
authors.lastname: Chida
authors.forename: Diana
authors.initials: D
authors.lastname: Adlowitz
authors.forename: Lin
authors.initials: L
authors.lastname: Silver
authors.forename: Erin
authors.initials: E
authors.lastname: Fox
authors.forename: Scott A
authors.initials: SA
authors.lastname: Jenks
authors.forename: Elise
authors.initials: E
authors.lastname: Palmer
authors.forename: Youliang
authors.initials: Y
authors.lastname: Wang
authors.forename: Jamie
authors.initials: J
authors.lastname: Heimburg-Molinaro
authors.forename: Quan-Zhen
authors.initials: QZ
authors.lastname: Li
authors.forename: Chandra
authors.initials: C
authors.lastname: Mohan
authors.forename: Richard
authors.initials: R
authors.lastname: Cummings
authors.forename: Christopher
authors.initials: C
authors.lastname: Tipton
authors.forename: Ignacio
authors.initials: I
authors.lastname: Sanz
mesh_terms: D000974:Antibodies, Antinuclear / Q000276:immunology; D017209:Apoptosis / Q000276:immunology; D001324:Autoantigens / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology*; D002308:Cardiolipins / Q000276:immunology; D002843:Chromatin / Q000276:immunology; D004247:DNA / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology*; D007130:Immunoglobulin Idiotypes / Q000276:immunology; D007135:Immunoglobulin Variable Region / Q000235:genetics / Q000276:immunology*; D008180:Lupus Erythematosus, Systemic / Q000276:immunology*; D008969:Molecular Sequence Data
chemical_list: D000974:Antibodies, Antinuclear; D001324:Autoantigens; D002308:Cardiolipins; D002843:Chromatin; D007074:Immunoglobulin G; D007130:Immunoglobulin Idiotypes; D007135:Immunoglobulin Variable Region; D004247:DNA